Upgrade does not work

[PeterRL1 0]

I have had Nitro for many years but a change in PC seems to have wiped it from existence. The only evidence I have is a receipt back in 2011 for an upgrade to Pro v7. Can I use this to upgrade to current version? I may have upgraded several times but cant find those receipts. 
Peter  

[AllainU 0]

Hello @PeterRL1,

Thank you for reaching out to us through our Community Forums!

To further assist you, could you please provide the serial number of your Nitro Pro you are having issue upgrading?

To send it via private message, hover your mouse on top of my name 'AllainU' and select 'Message'. 

Thank you very much in advance and I am looking forward to hearing back from you.